This invention relates to a hardness tester, more particularly, to a hardness tester which is preferably used for monitoring and setting a position to be measured on which an indentor bears a load.
Conventionally a well-known hardness tester has an arrangement in which a predetermined load is born on a material under test by an indentor in order to form a dent and hardness of the material is determined by a shape of the dent. With the hardness tester having the above arrangement, as described in Japan Utility Model laid open number 5-45964, the material under test is placed on a stage which can be transferred along the X and Y axes, a position to be measured is determined visually with making use of a microscope arranged above the stage and a dent is formed on the position of the material by an indentor.
The hardness tester having the above arrangement, however, has following problems.
1) In order to determine a position to be measured the stage has to be transferred on an X-Y plane. Then the larger a material under test becomes, the longer the length of transferring the stage becomes. Therefore X and Y stages become larger. The area of transferring the X and Y stages is about 4 times as large as the size of the material under test. PA0 2) Since distance between an indentor and a stage or distance between a microscope and a stage is adjusted by moving a Z stage up and down, it might happen that the hardness of the concave portion can not be measured. In addition, a teaching operation for setting a plurality of positions to be measured becomes complex if the material under test has a convex or concave portion. The conventional teaching operation is follows: Monitor a position to be measured on a material under test with making use of the microscope, and determine and store the position, then detach the object lens of the microscope from the material by lowering the stage to avoid a possible convex portion on the material. Next, transfer the stage along the X and Y axes and monitor a next position to be measured visually and determine the position. And then move the stage upward to a focusing area of the microscope, observe the surface of the material, and determine and store the position. PA0 3) In order to determine a position to be measured, adjust the virtual optical axis of the object lens of the microscope to a target position to be measured by transferring the stage along the X and Y axes. Then focus the microscope on the target position after the object lens is moved to approach the material and determine the target position by monitoring the position on the material. Since the stage is transferred so as to coincide the virtual optical axis of the object lens with the position to be measured visually, it takes long time or it may fail to determine the position to be measured with accuracy.